CVE-2011-3446 in Mac OS X
Summary
by MITRE
Apple Type Services (ATS) in Apple Mac OS X before 10.7.3 does not properly manage memory for data-font files, which allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted font that is accessed by Font Book.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/29/2021
Apple Type Services represents a critical component within macOS responsible for font handling and rendering operations across the operating system. This vulnerability exists in Mac OS X versions prior to 10.7.3 where the memory management implementation for data-font files within ATS contains a flaw that can be exploited remotely. The vulnerability specifically manifests when Font Book applications process maliciously crafted font files, creating a condition where improper memory handling leads to potential code execution or system instability. The flaw stems from inadequate bounds checking and memory allocation practices when processing font data structures, particularly affecting the way ATS manages memory for font resources during rendering operations. Attackers can leverage this vulnerability by creating specially crafted font files that, when opened or accessed through Font Book, trigger the memory corruption issue. This type of vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and CWE-129, which covers improper validation of array indices. The memory corruption occurs during font file parsing when ATS attempts to allocate memory for font data without proper validation of the font structure parameters, allowing attackers to manipulate memory layout through carefully constructed font content. The operational impact of this vulnerability extends beyond simple application crashes to potentially enable remote code execution, making it particularly dangerous in environments where users might encounter untrusted font files. When exploited, the vulnerability can cause arbitrary code execution with the privileges of the user running the Font Book application, or alternatively trigger denial of service conditions that prevent normal system operation. This vulnerability aligns with ATT&CK technique T1059.007, which covers execution through scripting, as the exploitation often involves font files that are processed through automated systems. The risk is elevated in enterprise environments where font files might be shared across systems or accessed through web-based applications. The vulnerability demonstrates a classic memory safety issue where insufficient input validation leads to exploitable memory corruption. The flaw affects not just Font Book but potentially any application that relies on ATS for font processing, including web browsers, document processors, and design applications. The exploitation requires minimal user interaction beyond opening or accessing the malicious font file, making it particularly dangerous in phishing scenarios or when users browse untrusted font repositories. Apple addressed this vulnerability through improved memory management routines in the ATS component, implementing stricter validation of font data structures before memory allocation occurs. The fix ensures proper bounds checking and memory boundary validation during font file processing, preventing attackers from manipulating memory layout through crafted font content. This vulnerability represents a significant concern for system security as font processing is a common operation across many applications and user workflows. The memory management flaw highlights the importance of proper input validation in system components that handle user-supplied data, particularly in font rendering systems where complex data structures must be parsed and processed. Security practitioners should prioritize patching this vulnerability in environments where font files might be encountered from untrusted sources, as the potential for remote code execution makes it a high-priority remediation. The vulnerability also underscores the broader challenge of securing font processing systems within operating systems, where font files can contain complex metadata and rendering instructions that must be safely parsed. Organizations should implement comprehensive font handling policies and consider restricting font file access to trusted sources. The remediation process involves updating to macOS 10.7.3 or later versions where Apple has implemented proper memory management controls for ATS font processing. This vulnerability serves as a reminder of the critical importance of memory safety in system components that process complex data formats, as even seemingly benign operations like font rendering can present significant security risks when proper validation controls are missing. The impact extends beyond immediate exploitation to long-term security implications, as compromised font processing systems can provide persistent access vectors for attackers seeking to establish footholds within operating system environments.